Re: Help! My Coil Blew Up

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Robert Jones" <alwynj48-at-earthlink-dot-net> 

Hi,

 > Original poster: "pjj" <tha3rdman-at-comcast-dot-net>
 >
 > I'm no expert, not even close but just from what I have read and correct
me
 > if I am wrong, but . . . A larger torrid would inhibit break out and I
don't
 > remember why but SSTC and ?VTTC? don't like that,  but that's just what I
 > remember reading and there-in lies 2 problems my memory, and word of
mouth.
 >
 > Paul

Yes your right. I should have added but not so big that break out is
inhibited.

Bob
 >
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Thursday, February 05, 2004 10:17 AM
 > Subject: Re: Help! My Coil Blew Up
 >
 >
 >  > Original poster: "Robert Jones" <alwynj48-at-earthlink-dot-net>
 >  >
 >  > Hi,
 >  >
 >  > I think you may need to give people a little more time to respond.
 >  >
 >  > I don't have any direct experience on SSTC.  Your failure sounds like
it
 >  > could be caused by a lot of things.
 >  >
 >  > I would expect the bigger the toroid the better to get your frequency
 > down.
 >  > Your frequency does seems high that maybe causing the unexpected
heating.
 >  > In any case if the fets are getting unexpectedly hot it indicates you
have
 > a
 >  > problem. I think you need clamping zeners too. Stick to 12v in till you
 > have
 >  > every thing looking right unless you have a bucket of new fets.  I also
 >  > suggest you run it of an external oscilator untill you have it all
checked
 >  > out and check the signal from your pick up.
 >  >
 >  > Your link down loads a file with an unknow extension??
 >  >
 >  > Bob
 >  >
 >  > ----- Original Message -----
 >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  > To: <tesla-at-pupman-dot-com>
 >  > Sent: Wednesday, February 04, 2004 7:48 PM
 >  > Subject: Re: Help! My Coil Blew Up
 >  >
 >  >
 >  >  > Original poster: "S.Gaeta" <sgtporky-at-prodigy-dot-net>
 >  >  >
 >  >  > I guess in spite of the age of the individuals involved, this SSTC
 > crowd
 >  > is
 >  >  > just another "old boys" club.
 >  >  >
 >  >  > I will get it working myself anyway. I have always gotten my
projects
 > to
 >  >  > work no matter what, and this will be no exception.
 >  >  >
 >  >  >
 >  >  > ----- Original Message -----
 >  >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  >  > To: <tesla-at-pupman-dot-com>
 >  >  > Sent: Tuesday, February 03, 2004 7:41 AM
 >  >  > Subject: Help! My Coil Blew Up
 >  >  >
 >  >  >
 >  >  >  > Original poster: "S.Gaeta" <sgtporky-at-prodigy-dot-net>
 >  >  >  >
 >  >  >  > I built Justin and Arons Quasi Self resonant coil, and it blew up
 >  > Friday
 >  >  >  > night.
 >  >  >  > Two mosfets failed. One was shorted and the other blew to bits.
Even
 >  >  > before
 >  >  >  > it blew up I was only getting 8" stremers out of it with 130 volt
 >  > input,
 >  >  > and
 >  >  >  > the fets ran hot. I checked the phasing of all the driver coils
and
 >  >  >  > everything looked right. The thing that was really disturbing was
 > that
 >  > I
 >  >  > was
 >  >  >  > getting ringing on the output of the H bridge even with a light
bulb
 > as
 >  > a
 >  >  >  > load, and 12 volts pure DC on the rails. Some pics of the coil,
and
 >  >  >  > waveforms can be seen at
 >  >  > http://community.webshots-dot-com/album/113763981zJBnik
 >  >  >  >
 >  >  >  > Well anyway, the two mosfets that shorted were not supposed to be
on
 > at
 >  >  > the
 >  >  >  > same time. The two that were bad would have placed a short right
 > across
 >  >  > the
 >  >  >  > DC buss. The other two tested good. It appears that the driver
 > survived
 >  >  > all
 >  >  >  > this mayhem. It puts out a good waveform with only the good fets
 >  > connected
 >  >  >  > to it. So at 8:15 PM, the cause of death was determined to be
shoot
 >  >  >  > through. Now I had 10 ohm resistors in series with each gate with
 > the
 >  >  >  > schottky across each one. It did improve the waveform, so the
only
 >  > thing
 >  >  > to
 >  >  >  > do now is try and improve the layout of the GDT and MOSFETs.
 >  >  >  >
 >  >  >  > I re-read the HV Guys instructions, and realised that I messed up
 > big
 >  > time
 >  >  >  > with the antenna. They say to put it no closer than 20" from the
 >  >  > secondary,
 >  >  >  > and I had mine maybe 6" away, so maybe having it too close may
have
 >  >  >  > introduced parasitics, or some other bad noise into the system. I
 > also
 >  >  > used
 >  >  >  > 13 turns on my GDT instead of 10 like they suggested. With my
 > resonant
 >  >  >  > frequency being around 236 KHz, which is a little on the high
side,
 > I
 >  >  > could
 >  >  >  > probably do better with less turns on the GDT. I also noticed
that
 > they
 >  >  >  > don't have a toroid in their photos. I used one because Dan's
SSTC
 > had
 >  >  > one,
 >  >  >  > but his circuit is also completely different than this one. Are
 > Toroids
 >  >  > bad
 >  >  >  > with this design?
 >  >  >  >
 >  >  >  > Has anyone else had problems with shoot through or cross
conduction?
 >  >  >  >
 >  >  >  > If anyone can offer me any further insight, or suggestions, I
would
 >  > really
 >  >  >  > appreciate it!
 >  >  >  >
 >  >  >  > Thanks,
 >  >  >  > Sue
 >  >  >  >
 >  >  >  >
 >  >  >
 >  >  >
 >  >
 >  >
 >  >
 >
 >